In a variety of applications, electrical (or galvanic) isolation is desired between distinct circuits while enabling communication between those circuits. “Galvanic isolation” means that there is no metallic or electrically conductive path between the distinct circuits. For example, galvanic isolation may be desired to protect a first circuit that operates at a relatively low supply voltage from a second circuit that operates at a relatively high supply voltage. In addition, galvanic isolation may be desired to isolate a first circuit tied to a first voltage reference (e.g., ground) from a second circuit tied to a different voltage reference (e.g., a floating voltage reference). Galvanic isolation also may be desired to prevent extraneous transient signals produced by one circuit from being conveyed to and processed by another circuit as valid signals or data.
A specific application that may benefit from galvanic isolation may be found within an automotive Hybrid Electronic Vehicle (HEV) system, for example. In an HEV system, a circuit that includes an insulated gate bipolar transistor (IGBT) array and corresponding gate drivers (referred to as an “IGBT circuit”) may be used to rectify AC power, and to provide the resulting DC power to a high voltage battery (e.g., 300 volts (V) or more). A grounded control circuit (e.g., including a microcontroller) operating at a significantly lower vehicle chassis voltage (e.g., 12 V) may be used to provide control signals to the gate drivers. In order to isolate the control circuit from switching noise from the IGBT circuit, it may be desirable to provide complete galvanic isolation between the control circuit and the IGBT circuit.
In other systems, for safety reasons, it may be desirable to isolate equipment that is connected to an AC power line from conductive portions of the equipment with which users may come into inadvertent physical contact. In such systems, an isolation circuit may be used to mitigate the likelihood of shocks, burns, and/or electrocution from current flowing through a human body to ground.
Conventional techniques for providing electrical isolation include the use of optical isolators, capacitive isolators, transformer-based isolators, and so on. However, these techniques may be non-optimal or unsuitable for some applications, in that they may be expensive, require a large amount of space, consume significant power, and/or have some other characteristics that may reduce their desirability for a given application.